Recently, a higher responsiveness and a higher integration of integrated circuits used for electronic devices such as computers, have been in greater demand. Accordingly, power consumption density of an integrated circuit has been increased, and the temperature of the electronic component in operation has been increased. In order to cool the electronic component, a radiating device such as a heat sink has been used.
FIG. 1 shows a conventional radiating device 2 placed on a semiconductor integrated circuit package 1. The radiating device 2 includes a thin rectangular base plate 3 which is in surface-contact with the top surface of the semiconductor integrated circuit package 1, and a number of fins 4 are erected on the top surface of the base plate 3 so as to increase the surface area of the radiating device. Typically, the radiating device 2 is made of aluminum. The heat of the semiconductor integrated circuit package 1 is transmitted to the radiating device 2, and is radiated to the atmosphere from the surface of radiating device 2.
FIG. 2 shows a conventional fin type radiating device 5. The radiating device 5 includes a circular base plate 6 which is in surface-contact with the top surface of the semiconductor integrated circuit package, and a plurality of fins 7 are erected on the top surface of the base plate 6 so as to increase the surface area of the radiating device. Typically, the radiating device 5 of this type is also made of aluminum.
In the conventional radiating device such as shown in FIGS. 1 and 2, the effect of radiation is improved by increasing the surface area. However, such conventional device does not provide a satisfactory cooling effect when used with electronic components that generate increased heat outputs and require a higher responsiveness and a higher integration and are in increased demand.
A heat pipe has been known as another example of a radiating device for cooling an electronic component. A heat pipe is obtained by reducing the inner pressure of an air tight container formed by closing both ends of a pipe, and by sealing a heat carrier such as water or alcohol in the enclosed space. The leaf carrier is called a working fluid. At a heated portion of the heat pipe, the fluid turns to steam or gas, the gas radiates heat when it moves away from the heated portion, and turns into liquid. The liquid returns to the heated portion because of capillary action. The heat is transmitted from the heated portion to the radiating portion by the repetition of this phenomenon.
A heat pipe is placed on a top surface of an electronic component in order to cool the electronic component such as a semiconductor integrated circuit package. Since the heat pipe is linearly in contact with the electronic component, it is inferior in its heat transmission efficiency from the electronic component to the heat pipe.
A heat pipe having a flat shape has been known. However, the heat receiving surface of even such a heat pipe is not a perfect flat plane but a curved or rough plane. Therefore, even such a heat pipe having a flat shape is inferior in its efficiency of heat transmission from the heated component to the heat pipe.
Fins have been attached to the heat radiating portion of the heat pipe in order to improve the heat radiation of the heat pipe. Typically, a sleeve having a large number of fins on its outer surface is attached to the heat radiating portion of the heat pipe. Such a sleeve with fins is adhered and fixed on the heat radiating portion of the heat pipe by using, e.g. an adhesive. Alternatively, the heat pipe is inserted with pressure and fixed in the sleeve with fins.
When the sleeve with fins and the heat pipe are adhered and fixed by using an adhesive, a heat transmission loss is caused in the adhesive. When the heat pipe is inserted with pressure in the sleeve with fins, there is an unavoidably small gap between the sleeve and the pipe, and a heat transmission loss is caused in this gap.